The invention concerns an acousto-optic device made from an optically birefringent crystal and suitable for deflecting the light beams and for optical processing of information. The acousto-optic device operates on the principle of the diffraction of light by acoustic waves and makes use of the simultaneous passive splitting of the ordinary and extraordinary light beams in an optically anisotropic crystal.
There was reported an acousto-optic device made from a single crystal of univalent mercury halide, as described by C. Barta et al in CSSR (Czechoslovakia) Author's Certificate No 170 007 , in which the elastic wave propagates in the [100 ] direction and the light wave in the [001] direction. This acousto-optic device distinguishes itself by a high value of the acousto-optic interaction, a broad range of optical transmission and by a low damping of the acoustic wave. A disadvantage of this device is the need of an additional polarizer when working with unpolarized light entering the acousto-optic device, e.g. in using most of the solid state lasers. A further disadvantage consists in the high sensitivity of the device to the real structure of the crystal, that manifests itself in the parasitic background of the diffused light and in the impairment of optical resolution. This leads to the necessity of stringent selection and hence to lower yield in the manufacture of acousto-optical devices of this type. Similar problems occur also with other acousto-optic devices based on other birefringent crystals, such as TeO.sub.2, PbMoO.sub.4 and others.